UPSC solved previous year questions

UPSC Science and technology PYQ with Answers

144 solved Science and technology questions from previous UPSC papers, each with an answer and explanation.

Questions
144
Years covered
2016–2026
Exam years
11
With answers
144

Science and technology questions by year

UPSC Science and technology PYQ with Answers

1–20 of 31
  1. Q1 2025 Mains GS3

    The fusion energy programme in India has steadily evolved over the past few decades. Mention India’s contributions to the international fusion energy project-International Thermonuclear Experimental Reactor (ITER). What will be the implications of the success of this project for the future of global energy? (Answer in 150 words)

    Answer explanation

    Introduction ITER seeks to demonstrate sustained deuterium-tritium fusion and scientific feasibility of fusion power. India’s contribution India joined ITER as a full partner through the Institute for Plasma Research.…

    Energy securityIterNuclear fusion
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  2. Q3 2025 Mains GS3

    India aims to become a semiconductor manufacturing hub. What are the challenges faced by the semiconductor industry in India? Mention the salient features of the India Semiconductor Mission. (Answer in 250 words)

    Answer explanation

    Introduction Semiconductors underpin digital infrastructure, defence, automobiles and clean technologies; manufacturing requires an exceptionally reliable ecosystem.…

    ElectronicsIndia semiconductor missionScience and technology
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  3. Q4 2025 Prelims GS

    With reference to 'Direct Air Capture', an emerging technology, which of the following statements is/are correct? I. It can be used as a way of carbon sequestration. II. It can be a valuable approach for plastic production and in food processing. III. In aviation, it can be a source of carbon for combining with hydrogen to create synthetic low-carbon fuel. Select the correct answer using the code given below.

    1. I and II only
    2. III only
    3. I, II and III✓
    4. None of the above statements is correct
    Answer explanation

    I, II and III Direct Air Capture (DAC) technology extracts CO2 directly from ambient air, which can be sequestered underground (carbon sequestration, I), used as a carbon feedstock in industrial processes such as plastics and food…

    Direct air captureEnvironmentScience and technology
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  4. Q5 2025 Prelims GS

    Consider the following pairs (Plant : Description): I. Cassava : Woody shrub II. Ginger : Herb with pseudostem III. Malabar spinach : Herbaceous climber IV. Mint : Annual shrub V. Papaya : Woody shrub. How many of the above pairs are correctly matched?

    1. Only two
    2. Only three✓
    3. Only four
    4. All five
    Answer explanation

    Only three Cassava is indeed a woody shrub (I correct), ginger is a herb with a pseudostem-like rhizomatous growth (II correct), and Malabar spinach is a herbaceous climbing vine (III correct).…

    BotanyPlantsScience and technology
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  5. Q6 2025 Prelims GS

    Consider the following types of vehicles: I. Full battery electric vehicles II. Hydrogen fuel cell vehicles III. Fuel cell-electric hybrid vehicles. How many of the above are considered as alternative powertrain vehicles?

    1. Only one
    2. Only two
    3. All the three✓
    4. None
    Answer explanation

    All the three All three vehicle types listed—full battery electric vehicles, hydrogen fuel cell vehicles, and fuel cell-electric hybrid vehicles—use non-conventional powertrains (as opposed to internal combustion engines) and are…

    Electric vehiclesScience and technology
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  6. Q7 2025 Prelims GS

    With reference to Unmanned Aerial Vehicles (UAVs), consider the following statements: I. All types of UAVs can do vertical landing. II. All types of UAVs can do automated hovering. III. All types of UAVs can use battery only as the source of power supply. How many of the statements given above are correct?

    1. Only one
    2. Only two
    3. All the three
    4. None✓
    Answer explanation

    None Not all UAVs can perform vertical landing (fixed-wing UAVs require runway-style landings), not all can hover (fixed-wing types cannot), and not all UAVs use only batteries (many use fuel-powered engines, especially larger/longer-range…

    DronesScience and technologyUav
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  7. Q8 2025 Prelims GS

    In the context of electric vehicle batteries, consider the following elements: I. Cobalt II. Graphite III. Lithium IV. Nickel. How many of the above usually make up the cathode of the battery?

    1. Only one
    2. Only two
    3. Only three✓
    4. All the four
    Answer explanation

    Only three In common lithium-ion EV battery chemistries (e.g., NMC - Nickel Manganese Cobalt), the cathode is typically composed of lithium along with cobalt and nickel. Graphite, however, is primarily used in the anode, not the cathode.…

    Battery chemistryEv batteriesScience and technology
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  8. Q10 2025 Prelims GS

    What is the common characteristic of the chemical substances generally known as CL-20, HMX and LLM-105, which are sometimes talked about in media?

    1. These are alternatives to hydrofluorocarbon refrigerants
    2. These are explosives in military weapons✓
    3. These are high-energy fuels for cruise missiles
    4. These are fuels for rocket propulsion
    Answer explanation

    These are explosives in military weapons CL-20, HMX, and LLM-105 are all high-energy chemical compounds used as explosives in military ordnance and weapons systems, valued for their high energy density and (in the case of insensitive…

    DefenceExplosivesScience and technology
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  9. Q11 2025 Prelims GS

    Consider the following statements: I. It is expected that Majorana 1 chip will enable quantum computing. II. Majorana 1 chip has been introduced by Amazon Web Services (AWS). III. Deep learning is a subset of machine learning. Which of the statements given above are correct?

    1. I and II only
    2. II and III only
    3. I and III only✓
    4. I, II and III
    Answer explanation

    I and III only The Majorana 1 chip, aimed at enabling scalable quantum computing using topological qubits, was introduced by Microsoft, not Amazon Web Services, so Statement II is incorrect.…

    AiQuantum computingScience and technology
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  10. Q12 2025 Prelims GS

    With reference to monoclonal antibodies, often mentioned in news, consider the following statements: I. They are man-made proteins. II. They stimulate immunological function due to their ability to bind to specific antigens. III. They are used in treating viral infections like that of Nipah virus. Which of the statements given above are correct?

    1. I and II only
    2. II and III only
    3. I and III only
    4. I, II and III✓
    Answer explanation

    I, II and III Monoclonal antibodies are laboratory-engineered (man-made) proteins designed to bind specifically to target antigens, thereby triggering or supporting immune responses, and they have been used/explored as treatments for viral…

    BiotechnologyMonoclonal antibodiesScience and technology
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  11. Q13 2025 Prelims GS

    Consider the following statements: I. No virus can survive in ocean waters. II. No virus can infect bacteria. III. No virus can change the cellular transcriptional activity in host cells. How many of the above statements are correct?

    1. Only one
    2. Only two
    3. All the three
    4. None✓
    Answer explanation

    None All three statements are factually incorrect: viruses do survive and are abundant in ocean waters; bacteriophages are viruses that specifically infect bacteria; and many viruses do alter/hijack the host cell's transcriptional…

    BiologyScience and technologyVirology
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  12. Q14 2025 Prelims GS

    Consider the following statements: Statement I: Some rare earth elements are used in the manufacture of flat television screens and computer monitors. Statement II: Some rare earth elements have phosphorescent properties. Which one of the following is correct in respect of the above statements?

    1. Both Statement I and Statement II are correct and Statement II explains Statement I✓
    2. Both Statement I and Statement II are correct but Statement II does not explain Statement I
    3. Statement I is correct but Statement II is not correct
    4. Statement I is not correct but Statement II is correct
    Answer explanation

    Both Statement I and Statement II are correct and Statement II explains Statement I Certain rare earth elements possess phosphorescent (light-emitting) properties (Statement II), which is precisely why they are used as phosphors in the…

    Rare earth elementsScience and technology
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  13. Q15 2025 Prelims GS

    Consider the following statements: I. Indian Railways have prepared a National Rail Plan (NRP) to create a 'future ready' railway system by 2028. II. 'Kavach' is an Automatic Train Protection system developed in collaboration with Germany. III. 'Kavach' system consists of RFID tags fitted on track in the station section. Which of the statements given above are not correct?

    1. I and II only✓
    2. II and III only
    3. I and III only
    4. I, II and III
    Answer explanation

    I and II only Indian Railways' National Rail Plan targets creating a future-ready railway system by 2030, not 2028, making Statement I incorrect.…

    Indian railwaysKavachScience and technology
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  14. Q16 2025 Prelims GS

    Consider the following space missions: I. Axiom-4 II. SpaDeX III. Gaganyaan. How many of the above space missions encourage and support microgravity research?

    1. Only one
    2. Only two
    3. All the three✓
    4. None
    Answer explanation

    All the three Axiom-4 (a commercial crewed mission to the ISS involving an Indian astronaut), SpaDeX (ISRO's Space Docking Experiment, a precursor to future in-orbit/space station activities), and Gaganyaan (India's human spaceflight…

    IsroScience and technologySpace missions
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  15. Q17 2025 Prelims GS

    Artificial way of causing rainfall to reduce air pollution makes use of

    1. silver iodide and potassium iodide✓
    2. silver nitrate and potassium iodide
    3. silver iodide and potassium nitrate
    4. silver nitrate and potassium chloride
    Answer explanation

    silver iodide and potassium iodide Artificial rainfall (cloud seeding) commonly uses substances such as silver iodide and potassium iodide as cloud condensation/ice nuclei, which promote the formation of raindrops or ice crystals in…

    Air pollutionCloud seedingScience and technology
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  16. Q18 2025 Prelims GS

    GPS-Aided Geo Augmented Navigation (GAGAN) uses a system of ground-based stations to provide necessary augmentation. Which of the following statements is/are correct in respect of GAGAN? I. It is designed to provide additional accuracy and integrity. II. It will allow more uniform and high quality air traffic management. III. Its benefits will be available only in aviation but not in other modes of transportation. Select the correct answer using the code given below.

    1. I, II and III
    2. II and III only
    3. Only I
    4. I and II only✓
    Answer explanation

    I and II only GAGAN, India's satellite-based augmentation system, is designed to provide enhanced accuracy and integrity to GPS signals (Statement I correct) and enables more uniform, high-quality air traffic management (Statement II…

    GaganNavigationScience and technology
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  17. Q19 2024 Mains GS3

    What is the present world scenario of intellectual property rights with respect to life materials? Although, India is second in the world to file patents, still only a few have been commercialized. Explain the reasons behind this limited commercialization. (Answer in 150 words)

    Answer explanation

    Introduction Life-material patents sit at the intersection of innovation, public health, biodiversity and ethical limits on ownership of living resources.…

    BiotechnologyIntellectual propertyPatent commercialisation
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  18. Q20 2024 Mains GS3

    What is the technology being employed for electronic toll collection on highways? What are its advantages and limitations? What are the proposed changes that will make this process seamless? Would this transition carry any potential hazards? (Answer in 150 words)

    Answer explanation

    Introduction India primarily uses RFID-based FASTag for automatic toll deduction, while GNSS-based distance charging is proposed for more seamless collection.…

    Electronic tollingFastag and gnssScience and technology
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